Silver halide emulsions for color photography



Patented Jan. 9, 1940 UNITED STATES PATENT OFFICE SILVER. HALIDE EMULSIONS FOR COLOR PHOTOGRAPHY No Drawing. Application October 29, 1937, Serial No. 171,705. In Germany November 2, 1936 6 Claims.

Our present invention relates to color photography and more particularly to a photographic element for color forming development.

It is an object of the invention to provide a. process of producing certain new and useful dyestufi components.

A further object is to provide dyestuff components which while retaining their solubility in aqueous liquids, do not tend to diffuse into the developer or from-one to an adjacent emulsion layer.

A further object is the provision of a photographic silver halide emulsion suitable for color forming development, containing the new dyestuif components.

Further objects will be apparent from the following detailed specification.

For producing photographic pictures, particularly color pictures, silver halide emulsions are used which'contain dyestuff components. In these emulsion layers there may be produced by color forming development a color image by formation of an azo-dyestufi or, in another process, directly or indirectly by way of a silver image.

This invention is based on the observation that the amide-like derivatives of malonic acid constitute a group of very valuable dyestuff components. Among such derivatives of malonic acid there may be named: the symmetrical dianilide of malonic acid. the symmetrical diaminobenzoic acid malonide and its derivatives the phenylnucleus of which is substituted, such as for instance compounds corresponding with the following formulae:

( am-Q on o further coon C-NH t on; 00 on -coon and the unsymmetrical compounds which may be obtained, for example, by reaction of an amino-compound of the' semi-chloride of malonic acid ethyl ester and subsequent reaction of the ester group with a second amide. An example of these last named bodies is that obtainable by the reaction of the semi-chloride of 5 malonic acid ethyl ester with aniline and the subsequent reaction of the product with paraaminobenzoic acid ethyl ester in boiling xylene.

The aforesaid amide-like derivatives of malonic acid yield in color development, for example with the aid of amino-dimethyl-aniline as the developer, a yellow dyestufi image besides the silver image. The components may either be added to the emulsion or to the developer.

The compounds usedv in this. invention, however, are suitable also as azo-components for the process of U. S. Patents Nos. 1,758,572 and 2,179,228. Or the components may be converted into azo-dyes following development and fixing by treatment with a diazo compound such as a carbonic acid solution of tetrazotized benzidine disulfonic acid. There is thus produced in each emulsion layer together with a silver picture a dye-stuff in which no structure can be perceived by magnification. The film is then treated with a silver bleaching out bath, i. e. that described in British Patent 401,340 to produce the dye image. Advantageously the dyestuff components may be made fast to diffusion in gelatin by introduction into their molecule of suitable substituents which increase the molecular size of the dyestufi components substantially. According to U. S. Patent 2,179,238 suitable groups can be introduced into the dyestufi components to lend a substantive character to the molecule of the color former. As described in U. S. Patent 2,178,612 the dyestufi components may be made last to diflusion by 'the introduction of radicals of highly polymerized carboxylic acids or their derivatives. As described in U. S.

patent application Ser. No. 94,340 filed August 5, 1936 components fast to diffusion may be obtained by introducing carbon chains having more than 5 carbon atoms. Furthermore dyestufi components fast to difiusion may be made as described in U. S. Patent 2,179,244 by introduction of poly-peptide radicals and as described in U. S. patent application Ser. No. 159,518 filed August 17, 1937 by introduction of carbohydrate radicals and as described in the U. S. patent application Ser. No. 164,499 filed September 18, 1937 by introducing constituents or conversion products '01 natural resins and as described in the U. S. patent application Ser. No. 166,832 filed October 1, 1937 by introduction of sterol radicals. Finally I the dyestufl components of the present invention may be combined to form a chain molecule, as described in the U, S. patent application Ser. No. 171,701 filed October 28, 1937.

5 The following are examples of dyestufl components which are fast to diffusion:

1. The product of reaction of the semi-chloride of malonic acid ethyl ester with octylamine and the subsequent reaction of the ester group with aniline. I

- 2. The product of reaction of the semi-chloride of malonic acid ethyl ester with para-dodecylaniline and the subsequent reaction of this product with para-amino-benzoic acid ethyl ester followed by saponification of the ester group.

3. The product of reaction of malonic acid diethyl ester with 2 mol aminodiphenyl.

It is preferable to introduce into the molecule of the dyestufi component one or more groups which lend solubility in water, for example carboxyl groups, sulfonic acid groups and several hydroxy-groups. The dyestuif former may be added to the emulsion at any desired point of the production thereof. The components are dissolved in water and methanol with an addition of alkali and added to the emulsion; about 2 grams of the dyestufi components are added to 1 kilo of the emulsion.

The silver halide emulsions carrying the color formers fast to diifusion may be worked up in any known manner to produce photographic layers and one or more of these may be arranged on one or both sides in superposition on the carrier. The layers may be used for the production SI of black-and-white or color images. For the purpose of color photography the layers are preferably sensitized for different regions of the spectrum. If desired dyestuif components, in addition to those of the present invention, may be incorporated in a layer.

For certain purposes it is advantageous to select the dyestuff components for the purpose of obtaining a neutral gray image.

The emulsions may, however, be worked up in other ways, for example diflferently sensitized emulsions having different color formers may be distributed on the carrier in the-form of small particles.

In the exposed emulsion layer the image may be produced either by simple or color forming development or by the reversal process as described in U. S. Patent 2,179,234. Or the picture may be produced in multi-layer material, each layer containing one of said dyestuif components, by ex- 55 posing the material, developing to black and white, in for instance Amidol, dissolving silver from the negative so produced by bleaching in for example a chromic acid bath, forming images in the remaining silver halide, developing in a developer such as is used above, forming silver halide images by treatment in a bleaching bath, i. e. again of chromic acid, forming latent images, transforming the images into silver and color images in a developer capable of forming dyestuffs with said dyestuif component, removing the developed silver and fixing in thiosulfate.

In the production of color images the silver is in most cases removed completely. In the production of black-and-white images with the aid of this invention the silver may be removed or may remain with the dyestufi imagein the layer. In certain cases it is preferable that the silver should remain wholly or in part in the layer.

What we claim is:

1. A light-sensitive photographic element comprising a support and at least one-silver halide emulsion containing a color former fast to diffusion said color former being a product of reaction of a compound selected from the group consisting of malonic acid, its halides and its esters, with an aliphatic amine containing a carbon chain of more than five carbon atoms.

2. A light-sensitive photographic element comprising a support and at least one silver halide emulsion containing a color former fast to diffusion said color former being a product of reaction of a compound selected from the group consisting of malonic acid, its halides and its esters, with an amine containing a substantive group.

3. A light-sensitive photographic element as.

defined in claim 1 wherein said mine is octylamine.

4. A light-sensitivephotographic element comprising a support and at least one silver-halide emulsion containing a color former fast to diffusion, said -color former being N-octyl-N'-phenyi-malondiamide.

5. A light-sensitive photographic element comprising a support and at least one silver-halide emulsion containing a color former fast to diffusion, said color former being N-p-dodecylphenyl-N-p-carboxyphenyl-malondiamide.

6. A light-sensitive photographic element comprising a support and at least one silver-halide emulsion containing a color former fast to diffusion, said color former being malondiphenylamide.

WILHELM SCHNEIDER.

ALFRED FROHLICH. 

